Starting
and charging systems on today's cars and trucks have evolved into high-tech
devices just as have many other automotive components.
Charging
systems, for example, interface with the PCM or BCM, which control generator
output with several charging modes that can shut off various loads under
different conditions, delivering improved battery and generator life as well as
increased fuel economy.
These
high-tech systems require in-depth diagnosis before replacement, including
checking other components and conditions that might affect system performance,
such as any Diagnostic Trouble Codes, fluid contamination, and battery health.
Charging
System
Charging
system testing is critical prior to replacing a generator in order to prevent
repeat generator failure. The following are some key items to check:
·
Perform a generator
output test according to the Service Information. The typical charging system
voltage at 77 degrees F is 13.5 to 15.2 volts.
·
Perform voltage drop
tests of the insulated and ground side of the generator (with the engine at
2,000 RPM, 0.2 volt maximum).
·
Check Diagnostic Trouble
Codes (DTCs) if the charging system is controlled by a PCM or BCM.
·
Check the insulator on
the generator battery post. A damaged insulator can lead to a short-to-ground
condition. (Fig. 13)
·
Check accessory drive
belts and tensioners for excessive wear.
Starter
Diagnosis
Starter
system testing begins with the battery. Proper starter solenoid and starter
operation depend on a healthy battery and good cable connections. Diagnosis
should include the following:
·
Check the available
voltage to the starter during cranking at the solenoid to see if battery
voltage is passing through the ignition switch circuit. A weak starter motor
may not be able to crank the engine fast enough to build compression and start
the engine.
·
If there is noise at the
starter motor or the starter spins but the engine does not crank, make sure the
starter is properly mounted and connections are tight. Also check the flywheel
or flexplate starter ring gear for damage.
·
If a starter motor is
equipped with a heat shield, make sure that the heat shield is installed (Fig. 14, A) or damage may occur. (Fig. 14, B) Some replacement starter motors are
equipped with a heat shield, while others require that the heat shield is
transferred from the original starter motor.
Battery
Performance
Test
the battery to determine its state of health. If the battery is faulty or there
is a parasitic drain (typically less than 30 mA), the generator could be short
lived or enough voltage may not be getting to the starter during cranking.
Fluid
Contamination
If
a generator or starter has evidence of fluid contamination, such as oil or
engine coolant, locate and correct the source of contamination to prevent
premature failure of the new component.
Learn More
For more information about charging and starting
systems, attend the Advanced Charging and Starting Systems Diagnostics seminar
(SS-EL-01.02). Contact your local ACDelco distributor to learn when the seminar
will be held in your area.
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Thanks to Mike Militello
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